Field of the Invention
The present invention relates to a lithography apparatus and an article manufacturing method.
Description of the Related Art
In semiconductor exposure apparatuses, the position in the translation direction of an original stage and a wafer (substrate) stage is precisely controlled using a laser length measuring machine in order to achieve a highly precise resolving power. Furthermore, regarding the vertical direction of the original stage and the wafer stage, the distance and the tilt between a wafer face and an optical system image face are measured using a focus sensor, and the wafer stage is driven for scanning. At that time, the drive is sequentially controlled in the Z (focus) direction and the tilt direction in order to cause the wafer face match the image face simultaneously when driving the wafer stage for scanning.
However, if a wafer is placed and exposure is started in a state where a foreign substance has adhered to a wafer chuck, which is a substrate holder, the image is locally defocused, and a resolution failure may occur. Examples of the foreign substance include resist that was removed from a wafer and has adhered to the wafer chuck. If a resolution failure is caused by a foreign substance during exposure, the yield in the chip production may be lowered.
Accordingly, on production site of semiconductors, much attention is paid particularly to such foreign substances on a wafer chuck, and countermeasures are taken, such as regularly cleaning the chuck using a cleaning unit. Furthermore, wafer exposure processing is performed between intervals of regular wafer chuck cleaning.
Highly adhesive foreign substances such as resist residue may not be removed merely by polish cleaning. Also in a case where contact with the wafer chuck is insufficient due to warping of the cleaning plate or manufacturing errors and polishing cannot be sufficiently performed, foreign substances may not be removed. If the production is continued without removing foreign substances, the foreign substances are detected in each lot, and the production is temporality stopped and cleaning operation is executed, so that the productivity is lowered.
Japanese Patent Laid-Open No. 7-066114 discloses control in which, if a foreign substance on a wafer holder is not removed even by cleaning of the wafer holder, a warning is issued and the procedure does not advance to exposure processing.
According to Japanese Patent Laid-Open No. 7-066114, if a warning is issued, the procedure does not advance to the exposure processing unless the foreign substance is removed. Thus, the substrate holder has to be detached from the apparatus and cleaned in an external cleaning apparatus such as a washing machine so that the foreign substance is removed, and, thus, the apparatus has to be stopped for several hours to a whole day.
Meanwhile, preventing the productivity from being lowered to the extent possible is also an important demand in the semiconductor manufacture.